Filter elements find application in the removal of various types of contaminants from gaseous or liquid fluid streams.
One application is in filtering combustion air before its delivery to an internal combustion engine. A typical source for combustion air is air drawn from outside of the vehicle, which commonly includes particulate contaminants present in the operating environment. An air cleaner which includes an air filter element is normally provided in the air induction system so as to capture these particulate contaminants, removing them from the air flow stream before the combustion air is delivered to the vehicle engine.
Filters are provided with filter media generally configured to have relatively small air flow permeable pores. The size of the pores are sized to permit the air flow or fluid stream to pass as freely as possible while being sufficiently small in size so as to block the passage of undesired particulate contaminants. Pleated filter media is often used in air filter applications. Typically the pleated media is provided in a flat rectangular shaped filter element. A gasket is typically formed about the periphery of the filter media and is configured for sealing against a filter element housing, such as an air cleaner housing.
In the case of an air filter, the presence of a filter media in the intake air stream acts to restrict air flow and thereby has a secondary effect of producing a pressure differential or pressure drop between the filter element inlet and outlet faces (i.e. across the filter media of the filter element). The pressure drop is related to the mass air flow and also related to the amount of accumulated occlusion or blockage of the air filter media. This air flow induced pressure drop acts to create deflection forces in the filter media of the filter element. These deflection forces are aligned with the air flow direction and, (for example) in pleated panel type air filters, the deflection forces are typically normal to plane defined by the filter element media. These deflection forces tend to distort or deform the filter media from its original unstressed shape.
Air filter elements are often made of pleated filter paper media as folded or pleated filter elements are relatively inexpensive and are easily produced. In automotive air filter applications, the pleated filter media may be secured to a periphery support frame, such as a molded plastic or elastomeric frame that is configured to support and provide a periphery seal to the filter element within an air cleaner housing. Pleating the filter paper media in a given size filter element increases the available filter surface area, while the folded “V” shaped or zig-zag pleats provide additional structural support to the filter media of the filter element against deformation or deflection due to air flow induced forces. In normal operating conditions, the inherent stiffening provided by the “V” shaped pleats in the filter media may be sufficient to resist the deflective forces of the filtered fluid stream.
In some operating conditions, however, the structural strength provided by the filter media pleats may be insufficient to support the filter media and prevent possible media failure. One example may be when a vehicle engine together with its associated induction air filter is operated in adverse weather conditions. Operation in an adverse climate can substantially increase deflection force loading on the media of the filter element. In cold climates the air filter may draw in accumulations of snow and ice pellets. The passage of drawn-in snow is blocked by the filter element and therefore accumulates at the dirty side (or inlet face) of the filter element, acting to further block air flow through the filter element thereby increasing the pressure drop across the filter element together with an increase in deflection forces acting upon the filter media. Similarly, some varieties of filter media are hydrophilic while some other types are hydrophobic. Hydrophilic media such as types of filter paper are prone to absorbing water droplets from the intake air stream, for example if operated in rainy or dense fog conditions. Water may wet the filter media; obstructing air flow pores in the media resulting in a further obstructed air flow through the media with the resultant further increase in pressure drop and resultant deflection forces and undesired deformation of the filter media.
Filter media may also become unduly obstructed with particulates due to extended operating intervals between maintenance and change out or alternately due to operation in dust laden environments. Particulates and debris accumulate on the air filter media at the filter inlet face increasing the occlusion of the filter media thereby reducing the air flow permeable area of the filter with a resulting increase in the pressure drop across the filter media.
In the art it is known to provide glue beads (also known as adhesive beads) arranged to bridge across and between filter media pleats to address some of these issues. An adhesive such as hot melt glue has been used to provide the beads. The glue beads help to lock the pleats into place, provide additional structural support to the filter element pleats and improve the resistance of the pleats to folding (one pleat folding onto an adjacent pleat) as well as resistance to deformation or crowning of the filter media. Multiple adhesive or glue beads may be applied to the pleated filter media, typically in a spaced parallel relationship extending across the pleats. Unfortunately, filter media is typically formed of filter media varieties affected by exposure to moisture, for example varieties of filter paper. This being the case, such filter media are still preferred as they are effective filtering agents and low in cost. The presence of water may weaken the filter media and compromise the adhesive binding of the glue beads to the pleated filter media, or result in localized tearing or failure of the filter media when exposed to air flow pressure forces. Additionally, glue beads are typically of the “hot melt” variety and hence are weakened or compromised by exposure to elevated temperatures such as may be experienced in the engine compartment of a motor vehicle. Such beads may “age” over time and become brittle and crack. Cracks or gaps compromise the ability of the glue beads to carry tensile loads such as required to resist filter media deformation or crowning. Even in non-adverse conditions glue beads provide a less than ideal solution to filter media deformation and filter media support problems discussed above, so the problem remains.
As can be seen, there remains a need in the art for a support apparatus to provide supplemental support to the filter media, thereby overcoming problems in the prior art filter elements, including those with varieties of glue bead stiffeners. Preferably this support apparatus solves the problems identified above, is usable with currently available varieties of filter elements, and can be realized without unduly increasing air cleaner or filter element cost or complexity.